I know there is plugin by ZT (http://www.vbulletin.org/forum/showthread.php?t=96190) but it doesn't work with big usergroups and plugin is unsupported so this is request for some fix or another plugin or something.

Before ZT's hack I used another one but I can not remember who was author of that hack and can't find it now. If anyone have it please let me know.